Virology Practice Questions

Q: Which adenovirus types are known causes of infantile diarrhea?

Types 40, 41. **Explanation:** Adenoviruses are double-stranded DNA viruses classified into several subgroups (A–G). While most adenoviruses are associated with respiratory or ocular infections, specific types are **enterotropic**. **1. Why Option C is Correct:** Adenovirus **Types 40 and 41** (belonging to **Subgenus F**) are known as the **"Enteric Adenoviruses."** They are a leading cause of acute infantile gastroenteritis worldwide, second only to Rotavirus. Unlike other adenoviruses, types 40 and 41 are difficult to culture in standard cell lines and are primarily diagnosed via stool antigen detection (ELISA) or PCR. **2. Analysis of Incorrect Options:** * **Option A (Types 3, 4, 7):** These are primarily associated with **Acute Respiratory Disease (ARD)** and Pharyngoconjunctival fever. Type 7 is also a common cause of severe pneumonia in children. * **Option B (Types 8, 19, 37):** These are the classic causes of **Epidemic Keratoconjunctivitis (EKC)**, characterized by "shipyard eye" and subepithelial corneal infiltrates. * **Option D (Type 37):** As mentioned above, this is associated with ocular infections and is also a recognized cause of viral urethritis/cervicitis. **High-Yield Clinical Pearls for NEET-PG:** * **Intussusception:** Adenovirus infection can cause mesenteric lymphadenitis, which acts as a lead point for intussusception in children. * **Hemorrhagic Cystitis:** Types **11 and 21** are high-yield causes of acute hemorrhagic cystitis in children. * **Inclusion Bodies:** Look for **"Smudge cells"** (large, intranuclear basophilic inclusions) in histopathology. * **Structure:** They possess a unique **Penton fiber** projecting from the capsid, which acts as a hemagglutinin and mediates cell attachment.

Q: Which of the following clinical specimens is used for the detection of BK polyomavirus by electron microscopy?

Urine. **Explanation:** **BK Polyomavirus** is a double-stranded DNA virus that remains latent in the renal tubular cells and uroepithelium after primary infection (usually acquired in childhood). In immunocompromised individuals, particularly **renal transplant recipients**, the virus reactivates, leading to **BK virus-associated nephropathy (BKVAN)** or hemorrhagic cystitis. 1. **Why Urine is correct:** Since the virus replicates within the renal tubules and transitional epithelium, it is shed in high concentrations in the urine. Electron microscopy (EM) of the urine sediment can reveal characteristic **"Decoy cells"** (cells with large intranuclear inclusions) or the virus particles themselves, which typically exhibit a "honeycomb" or icosahedral appearance. While PCR is now the gold standard for quantification, EM of urine remains a classic diagnostic method described in textbooks. 2. **Why other options are incorrect:** * **Brain tissues:** This is the specimen of choice for **JC Virus**, another polyomavirus that causes Progressive Multifocal Leukoencephalopathy (PML). BK virus does not typically target the CNS. * **Blood:** While BK viremia is a marker for systemic reactivation and risk of nephropathy (detected via PCR), the viral load in blood is generally lower than in urine, making EM an inefficient tool for blood specimens compared to urine. **High-Yield Clinical Pearls for NEET-PG:** * **Mnemonic:** **B**K virus affects the **B**ladder and **K**idney; **J**C virus affects the **J**unction (CNS/Brain). * **Decoy Cells:** Found in urine cytology; they mimic carcinoma cells (hence the name) but represent viral cytopathic effects. * **BKVAN:** A major cause of graft rejection in renal transplant patients. * **Morphology:** Polyomaviruses are small, non-enveloped, icosahedral viruses (~45 nm).

Q: Cowdry type A inclusion bodies are seen in which of the following?

Herpesvirus. **Explanation:** **Cowdry Type A inclusion bodies** are characteristic histopathological findings seen in infections caused by the **Herpesviridae** family (including HSV-1, HSV-2, and VZV). These are **intranuclear, eosinophilic, "droplet-like" masses** surrounded by a clear halo (due to chromatin margination at the nuclear membrane). They represent sites of viral replication and protein assembly within the nucleus. **Analysis of Options:** * **Hepatitis B Virus (HBV):** Characterized by **"Ground-glass" hepatocytes**, which represent the accumulation of HBsAg in the smooth endoplasmic reticulum (cytoplasmic, not nuclear). * **Adenovirus:** Produces **Cowdry Type B** inclusion bodies (basophilic, "full" nucleus) or "Smudge cells." * **Poxvirus:** Being a DNA virus that replicates in the **cytoplasm**, it produces **Guarnieri bodies** (intracytoplasmic eosinophilic inclusions), notably seen in Variola and Vaccinia. **High-Yield Clinical Pearls for NEET-PG:** * **Cowdry Type A:** Seen in **Herpes Simplex**, **Varicella-Zoster**, and **Yellow Fever** (where they are specifically called **Torres bodies**). * **Tzanck Smear:** A rapid bedside test for Herpes where Cowdry Type A inclusions and **multinucleated giant cells** are visualized. * **Negri Bodies:** Pathognomonic intracytoplasmic inclusions found in the Purkinje cells of the cerebellum or hippocampus in **Rabies**. * **Owl’s Eye Appearance:** Large intranuclear inclusions characteristic of **Cytomegalovirus (CMV)**. * **Henderson-Paterson Bodies:** Large, eosinophilic intracytoplasmic inclusions seen in **Molluscum Contagiosum** (a Poxvirus).

Q: What is the most common cause of fulminant hepatitis in pregnancy?

Hepatitis E. ### Explanation **Correct Option: B. Hepatitis E** Hepatitis E Virus (HEV) is the most common cause of fulminant hepatic failure (FHF) in pregnant women, particularly during the **third trimester**. While HEV generally causes a self-limiting illness in the general population (mortality <1%), the case fatality rate in pregnancy can soar to **15–25%**. The underlying pathophysiology is attributed to a combination of high viral load, altered host immune response (Th2 shift), and hormonal changes (high progesterone levels) that promote viral replication and liver necrosis. **Analysis of Incorrect Options:** * **Hepatitis D (A):** HDV requires co-infection or super-infection with Hepatitis B. While it increases the severity of HBV, it is not the primary cause of pregnancy-related fulminant hepatitis. * **Hepatitis B (C):** HBV is a common cause of chronic hepatitis and can cause acute liver failure, but it does not show the specific, disproportionate predilection for high mortality in pregnancy that HEV does. * **Hepatitis A (D):** HAV is transmitted via the feco-oral route and causes acute hepatitis, but it rarely progresses to fulminant liver failure in pregnant patients. **High-Yield Clinical Pearls for NEET-PG:** * **Virus Type:** HEV is a non-enveloped, single-stranded RNA virus (Hepeviridae family). * **Transmission:** Feco-oral route (water-borne outbreaks). * **Genotypes:** Genotypes 1 and 2 are associated with human epidemics in developing countries; Genotypes 3 and 4 are zoonotic (pigs). * **Diagnosis:** IgM anti-HEV is the gold standard for acute infection. * **Prognosis:** HEV does **not** cause chronic hepatitis in immunocompetent individuals (unlike HBV/HCV), but can cause chronicity in organ transplant recipients.

Q: What is the amplifier host in Japanese encephalitis?

Pig. **Explanation:** Japanese Encephalitis (JE) is a zoonotic viral infection caused by a Flavivirus. Understanding the transmission cycle is crucial for NEET-PG: * **Why Pig is the Correct Answer:** Pigs are the **amplifier hosts**. When a pig is infected, the virus undergoes rapid multiplication, leading to high-titer viremia (prolonged and intense levels of virus in the blood). This high viral load is sufficient to infect a biting mosquito, which then transmits the virus to humans. Pigs do not manifest clinical disease but act as a "reservoir-cum-amplifier." * **Analysis of Incorrect Options:** * **Man (Option A):** Humans are **dead-end hosts**. The level of viremia in humans is transient and insufficient to infect a mosquito. Therefore, man-to-man transmission does not occur. * **Culex mosquito (Option B):** These are the **vectors**. Specifically, *Culex tritaeniorhynchus* is the primary vector in India. They transmit the virus from the amplifier host to humans. * **Horse (Option D):** Like humans, horses are **dead-end hosts**. They can develop clinical encephalitis but do not contribute to the transmission cycle. **High-Yield Clinical Pearls for NEET-PG:** * **Natural Reservoir:** Water birds (Ardeid birds like Herons and Egrets). * **Primary Vector:** *Culex tritaeniorhynchus* (breeds in stagnant water/paddy fields). * **Seasonality:** Post-monsoon period. * **Vaccination:** Live attenuated **SA-14-14-2** (most common) or killed (JENVAC). * **Diagnosis:** IgM Capture ELISA (MAC-ELISA) of CSF or serum is the gold standard. * **MRI Finding:** Bilateral thalamic involvement (classic board-style presentation).

Q: An 18-year-old college student presents with a sore throat, fever, fatigue, and loss of appetite. Examination reveals pharyngitis with cervical lymphadenopathy. Blood tests show lymphocytosis and the presence of heterophile antibodies. Which of the following best describes the virus responsible for this illness?

Double-stranded, enveloped DNA virus. ### Explanation **Diagnosis: Infectious Mononucleosis (IM)** The clinical triad of fever, pharyngitis, and lymphadenopathy in a young adult, combined with **heterophile antibodies** (Monospot test positive) and lymphocytosis (atypical lymphocytes), is pathognomonic for Infectious Mononucleosis caused by the **Epstein-Barr Virus (EBV)** [1]. **1. Why Option A is Correct:** EBV is a member of the *Herpesviridae* family (specifically Human Gammaherpesvirus 4). All Herpesviruses share a specific structure: they are **double-stranded, linear DNA viruses** surrounded by an icosahedral capsid and a lipid **envelope** derived from the host nuclear membrane. **2. Why the Other Options are Incorrect:** * **Option B:** Nonenveloped DS-DNA viruses include Adenovirus and Papillomavirus. While Adenovirus causes pharyngitis, it does not typically produce heterophile antibodies or significant lymphocytosis. * **Option C:** This describes viruses like Influenza, HIV, or Paramyxoviruses (Mumps/Measles). While they cause systemic symptoms, their genomic structure does not match EBV [2]. * **Option D:** This describes Parvovirus B19 (the only medically significant SS-DNA virus), which causes Erythema Infectiosum (Slapped-cheek rash), not IM [3]. **Clinical Pearls for NEET-PG:** * **Atypical Lymphocytes:** These are actually **CD8+ T-cells** reacting against infected B-cells (Downey cells) [1]. * **Receptor:** EBV enters B-cells via the **CD21** receptor (also known as CR2). * **The "Ampicillin Rash":** If a patient with IM is mistakenly treated for strep throat with Ampicillin or Amoxicillin, they often develop a characteristic maculopapular rash [4]. * **Complications:** Splenic rupture (avoid contact sports) and associations with malignancies like Burkitt Lymphoma and Nasopharyngeal Carcinoma [1].

Q: An individual who uses intravenous drugs discovers that a friend with whom he shared needles for injections has been diagnosed with viral hepatitis. He has his blood tested for HBV. Which of the following viral markers is usually the first detected after infection with HBV?

HBsAg. **Explanation:** **1. Why HBsAg is the correct answer:** Hepatitis B Surface Antigen (**HBsAg**) is the hallmark of infection and the **first serological marker** to appear in the blood after HBV infection. It typically becomes detectable 1 to 10 weeks after exposure, often predating the onset of clinical symptoms and the rise in liver enzymes (ALT/AST). Its presence indicates that the individual is infectious. If HBsAg persists for more than 6 months, the infection is defined as chronic. **2. Why the other options are incorrect:** * **HBcAg (Hepatitis B Core Antigen):** This is a particulate antigen found within the hepatocyte. It is **not secreted into the blood** and therefore cannot be detected by routine serum assays. * **HBeAg (Hepatitis B e-Antigen):** This marker appears shortly after HBsAg. It signifies high levels of viral replication and high infectivity. While it appears early, it is almost always preceded by HBsAg. * **Anti-HBe:** These are antibodies produced against the e-antigen. Their appearance (seroconversion) usually indicates a transition to a lower state of viral replication. They appear much later in the course of the disease. **3. NEET-PG High-Yield Pearls:** * **Window Period:** The interval during which HBsAg has disappeared but Anti-HBs has not yet appeared. The only marker of acute infection during this time is **Anti-HBc IgM**. * **Indicator of Recovery:** The appearance of **Anti-HBs** (HBsAb) signifies immunity (either through recovery or vaccination). * **Best Indicator of Replication:** **HBV-DNA** (measured by PCR) is the most sensitive quantitative marker for viral load, but HBsAg remains the first protein marker detected. * **Sequence of appearance:** HBsAg → HBeAg → Anti-HBc → Anti-HBe → Anti-HBs.

Q: A 9-year-old male presents with a history of fever, nonspecific symptoms, bright red cheeks, and a macular lacy rash over his body. Which of the following viruses is the most likely cause of this disease?

Parvovirus B19. **Explanation:** The clinical presentation described—a 9-year-old with fever followed by **"bright red cheeks" (slapped-cheek appearance)** and a **macular lacy (reticular) rash** on the trunk and extremities—is classic for **Erythema Infectiosum**, also known as **Fifth Disease**. **Why Parvovirus B19 is correct:** Parvovirus B19 is a small, non-enveloped ssDNA virus. It infects and replicates in rapidly dividing erythroid progenitor cells in the bone marrow by binding to the **P-antigen** (globoside). The rash is immune-mediated (Type III hypersensitivity), appearing after the initial viremic phase has resolved, meaning the child is typically no longer contagious once the rash appears. **Why other options are incorrect:** * **HSV-1:** Typically presents with orolabial herpes (cold sores) or gingivostomatitis, not a diffuse lacy rash or slapped-cheek appearance. * **Rubella (German Measles):** Presents with a maculopapular rash that starts on the face and spreads cephalocaudally, often accompanied by characteristic **post-auricular or suboccipital lymphadenopathy**. * **Rubeola (Measles):** Characterized by the "3 Cs" (Cough, Coryza, Conjunctivitis) and **Koplik spots**. The rash is a confluent maculopapular eruption, not lacy. **High-Yield Clinical Pearls for NEET-PG:** * **Aplastic Crisis:** Parvovirus B19 can cause a life-threatening drop in hemoglobin in patients with high red cell turnover (e.g., Sickle Cell Anemia, Hereditary Spherocytosis). * **Hydrops Fetalis:** Infection during pregnancy can lead to severe fetal anemia and congestive heart failure. * **Arthropathy:** In adults, infection often presents as symmetrical small joint arthritis (mimicking Rheumatoid Arthritis). * **Receptor:** It uses the **P-antigen** on RBCs; individuals lacking this antigen are immune.

Q: Which of the following are transfusion-transmitted viruses?

All of the above. **Explanation:** Transfusion-transmitted infections (TTIs) are pathogens that can be inadvertently passed from a donor to a recipient through blood or blood products. For a virus to be efficiently transmitted via transfusion, it must typically have a phase of viremia (presence in the blood) and be capable of surviving storage conditions. * **Hepatitis B (HBV):** This is a classic TTI. Despite rigorous screening for HBsAg and increasingly for anti-HBc or HBV-DNA (NAT), it remains a risk due to the "window period" or occult infections. * **Cytomegalovirus (CMV):** CMV is a leukocyte-associated virus. It is a significant concern for immunocompromised patients and neonates. Risk is mitigated by using "leukoreduced" blood or CMV-seronegative units. * **HTLV-1 and HHV-8:** HTLV-1 (associated with Adult T-cell Leukemia/Lymphoma) is also cell-associated and screened in many countries. HHV-8 (Kaposi Sarcoma-associated Herpesvirus) can be transmitted via blood, particularly in endemic areas, though it is not universally screened. **Why "All of the above" is correct:** All the listed viruses have documented parenteral transmission routes and can persist in various blood components (plasma or cellular elements), making them potential TTIs. **High-Yield Clinical Pearls for NEET-PG:** * **Most common TTI globally:** Hepatitis B. * **Most common TTI in India:** Historically Hepatitis B, but risk is decreasing with NAT (Nucleic Acid Testing). * **Window Period:** The time between infection and detection. NAT significantly reduces this period compared to serology. * **Bacterial Contamination:** Platelets carry the highest risk of bacterial sepsis because they are stored at room temperature (20-24°C). * **Other TTIs:** HIV-1/2, Hepatitis C, Malaria, Syphilis, and emerging threats like Zika or West Nile Virus.

Q: Which of the following genes is associated with the encoding of reverse transcriptase?

Pol. The correct answer is **A. Pol**. ### **Explanation** The Human Immunodeficiency Virus (HIV) and other retroviruses possess three structural genes essential for their life cycle: **gag, pol, and env**. 1. **Pol (Polymerase) Gene:** This gene encodes the essential enzymes required for viral replication and integration. These include: * **Reverse Transcriptase:** Converts viral RNA into proviral DNA. * **Integrase:** Integrates the proviral DNA into the host cell genome. * **Protease:** Cleaves precursor polypeptides into functional proteins during viral maturation. 2. **Gag (Group-specific Antigen) Gene:** Encodes the inner structural proteins, primarily the **p24 capsid protein** (used for early diagnosis) and the p17 matrix protein. 3. **Env (Envelope) Gene:** Encodes the precursor glycoprotein **gp160**, which is cleaved by host proteases into **gp120** (attachment to CD4) and **gp41** (fusion and entry). 4. **LTR (Long Terminal Repeat):** These are non-coding sequences at both ends of the viral genome that act as promoters for gene transcription; they do not encode proteins. ### **High-Yield Clinical Pearls for NEET-PG** * **p24 Antigen:** The earliest serological marker of HIV infection (detected during the window period). * **gp120:** Responsible for tropism; it binds to the CD4 receptor and CCR5/CXCR4 co-receptors. * **Drug Targets:** * **NRTIs/NNRTIs** target Reverse Transcriptase. * **Raltegravir** targets Integrase. * **Maraviroc** targets the CCR5 co-receptor. * **Enfuvirtide** targets gp41 (fusion inhibitor).

Question 1

Which adenovirus types are known causes of infantile diarrhea?

Accepted Answer

Types 40, 41

Answer

Types 3, 4, 7

Answer

Types 8, 19, 37

Answer

Types 37

Question 2

Which of the following clinical specimens is used for the detection of BK polyomavirus by electron microscopy?

Accepted Answer

Urine

Answer

Brain tissues

Answer

Blood

Answer

None of the above

Question 3

Cowdry type A inclusion bodies are seen in which of the following?

Accepted Answer

Herpesvirus

Answer

Hepatitis B virus (HBV)

Answer

Adenovirus

Answer

Poxvirus

Question 4

What is the most common cause of fulminant hepatitis in pregnancy?

Accepted Answer

Hepatitis E

Answer

Hepatitis D

Answer

Hepatitis B

Answer

Hepatitis A

Question 5

What is the amplifier host in Japanese encephalitis?

Accepted Answer

Pig

Answer

Main

Answer

Culex mosquito

Answer

Horse

Question 6

An 18-year-old college student presents with a sore throat, fever, fatigue, and loss of appetite. Examination reveals pharyngitis with cervical lymphadenopathy. Blood tests show lymphocytosis and the presence of heterophile antibodies. Which of the following best describes the virus responsible for this illness?

Accepted Answer

Double-stranded, enveloped DNA virus

Answer

Double-stranded, nonenveloped DNA virus

Answer

Single-stranded, enveloped RNA virus

Answer

Single-stranded, nonenveloped DNA virus

Question 7

An individual who uses intravenous drugs discovers that a friend with whom he shared needles for injections has been diagnosed with viral hepatitis. He has his blood tested for HBV. Which of the following viral markers is usually the first detected after infection with HBV?

Accepted Answer

HBsAg

Answer

HBcAg

Answer

HBeAg

Answer

Anti-HBe

Question 8

A 9-year-old male presents with a history of fever, nonspecific symptoms, bright red cheeks, and a macular lacy rash over his body. Which of the following viruses is the most likely cause of this disease?

Accepted Answer

Parvovirus B19

Answer

Herpes simplex virus (HSV) type 1

Answer

Rubella virus

Answer

Rubeola (measles) virus

Question 9

Which of the following are transfusion-transmitted viruses?

Accepted Answer

All of the above

Answer

Hepatitis B

Answer

Cytomegalovirus (CMV)

Answer

Human T-lymphotropic virus 1 (HTLV-1) and Human herpesvirus 8 (HHV-8)

Question 10

Which of the following genes is associated with the encoding of reverse transcriptase?

Accepted Answer

Pol

Answer

Env

Answer

Gag

Answer

LTR

Virology — MCQs

Virology — MCQs

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